Variable area nozzles for jet propulsion systems



June 7, 1955 HQLL; ET AL 2,709,888

VARIABLE AREA NOZZLES FOR JET PROPULSION SYSTEMS Filed March 19, 1951FIG. I

M02. nvenors dub Attornty:

Unite VARIABLE AREA NQZZLES FOR JET FRUPULSEGN SYSTEMS Raymond Hell,Countesthorpe, Leicester, and William Deacon, Blaby, Leicester, England,assignors to Power Jets (Research and Development) Limited, London,England, a British company This invention is for improvements in orrelating to variable area nozzles for a jet propulsion system in whichthe jet is a stream of hot gaseous fluid.

The invention is concerned with a type of variable area nozzle for jetpropulsion in which variation is obtained by the use of obturating meansarranged at the boundary of the nozzle at the end of the jet pipe andconstructed for movement transversely of the jet stream to constrict it.This type of variable area nozzle has been found to be very eflectivebut difliculty has been experienced in achieving an acceptable degree ofoperational reliability due to thermal distortion of the parts and toundue leakage losses past the obturating means.

According to the present invention, in a variable area nozzle of thetype referred to, the obturator is supported, independently of theoutlet end of the nozzle by a supporting structure which leaves thenozzle portion free for thermal expansion and contraction independentlyof the obturator and its supporting structure. The supporting structurefor the obturating means may be a shroud pipe arranged around the nozzleportion of the jet pipe and lying substantially co-extensive therewith,the two forming together a double skin construction in which the outerand cooler shroud pipe carries the obturating means and actuatingmechanism whilst the inner and hot nozzle portion is free to expand andcontract independently of the outer shroud pipe. The outer shroud pipemay be constructed as a separable unit secured to the jet pipe and thenozzle portion may also be constructed as a separable unit, the twobeing substantially the same length and joined together to the jet pipeat a common junction point.

A form of the invention will now be described with reference to theaccompanying drawing in which:

Figure 1 is a side view of a variable area jet nozzle or orifice partlyin section showing the double skin construction of the jet pipe.

Figure 2 is an end view of Figure 1.

Figure 3 is a fragmentary view showing a carbon insert.

A jet pipe 1 is provided with a flange 2 to which is secured a flange 3of a short separable pipe unit 4 forming a convergent nozzle portion 5extending axially therefrom.

An outer shroud pipe unit 6 which surrounds the short separable pipeunit 4 is secured by its flange 7 to the flanges 2 and 3. T ne shroudpipe unit 6 is shown as a continuation of the jet pipe 1 and hassubstantially the same cross-sectional area. The two pipe units 4 and 6together form a double skin construction.

A pair of shroud rings 8 and 9 are secured to a flange l!) at the freeand unsupported outlet end of the shroud pipe unit 6 to position themwith the inneredge of the inner ring 3 adjacent to the free andunsupported end of the nozzle portion 5 leaving an annular gap 11 narrowenough to prevent leakage of jet fluid between the two pipe units 4 and6 but allowing free expansion and contraction of the pipe unit 4 and thenozzle portion 5.

States Patent 0 At least one pair of constrictor elements 13 of flatplate, shaped like a pair of outside calipers are arranged for movementbetween the shroud rings 8 and 9 about a pivot 14 so that their inneredges can move into and out of the jet stream issuing from the nozzle 5.The free ends of the constrictor elements 13 are each provided withfixed bosses 15 to each of which is pivotally secured a link 16. A pairof bell crank levers 17 pivoting at 18 are each pivotally connected byone of their lever ends to the link 16 whilst their other lever endscarry pivot bosses 19 engaging slots 20 in a member 21 carried by anactuating rod 22. The actuating mechanism of the constrictor elements 13is carried on the outer shroud pipe 6 together with the shroud rings 8and 9. The actuating mechanism is thus carried on a comparatively coolstructure whilst the nozzle portion 5, which is subjected to the hot jetfluid, can expand and contract freely and independently of the outershroud pipe 6.

A sealing ring 12 is arranged around the outer rims of the rings 8 and 9to seal the gap between them to prevent leakage of the jet fluid passingbetween them and the elements 13 when the elements 13 are projectinginto the stream.

In Figures 1 and 2 the elements 13 are shown in the constrictingposition. To move them to the open position the rod 22 is pushed to theright as viewed in Figure l which moves the member 21 engaging thebosses 19 causing the bell crank levers 17 to pivot on their pivots 13and push the two links 16 apart and causing the elements 13 to pivotabout their pivots 14 and recede between the rings 8 and 9. In anaircraft jet propulsion system the actuating rod 22 may be operated byhand or its operation may be by servo mechanism actuated by movementofthe power control lever of the power plant of the system and bymovement of the reheat control of the system if re-heat is used.

To afford satisfactory operation at the high temperatures associatedwith high thrust when re-heat is used, carbon inserts 24 are inserted inslots 25 formed in the outer ring 9 (see Figure 3) to reduce frictionand prevent picking-up between the ring 9 and the caliper elements 13.

When more than one pair of flat plate constrictor elements 13 are usedto control the area of the nozzle 5, the other pairs are being spacedappropriately to give a symmetrical jet stream.

What we claim is:

1. A variable outlet jet pipe unit for jet propulsion plant including incombination a nozzle, an obturator comprising a pair of elements wide inone dimension mounted at the outlet end of the nozzle for movement in aplane parallel to said one dimension and across the long axis of thenozzle partially to obstruct said nozzle, and substantially reduce theeffective crosssectional area thereof, and a supporting structureoutside the nozzle ttached to the unit remotely from the outlet end ofthe nozzle and supporting said obturator independently of said outletend, the nozzle being accordingly free for thermal expansion andcontraction independently of the said obturator and its supportingstructure.

2. A jet pipe according to claim 1 wherein the said supporting structureis a tubular shroud around the nozzle but independent thereof.

3. A variable outlet jet pipe unit for jet propulsion plant including incombination a nozzle, a calliper-type obturator mounted at the outletend of the nozzle, consisting of a pair of calliper arms movable towardseach other across the path of the jet stream in a plane substantiallyperpendicular to the axial centerline of the nozzle to obstruct saidnozzle, and decrease the effective cross-sectional area thereof toconstrict the jet, a pair of plates on opposite sides of said obturatorlocated outside of and free of the nozzle, said plates defining betweenthem a channel in which the calliper arms slide, and a support attachedto said plates and attached to the unit remotely from the outlet end ofthe said nozzle, the nozzle being accordingly free for thermal expansionand contraction independently of the said obturator and its supportingstructure.

4. A jet pipe unit according to claim 3 including a sealing ring in theform of a rim around the said plates, making up with these plates anannular channel enclosing the calliper arms.

5. A variable outlet jet pipe unit for jet propulsion plant including incombination a nozzle, a tubular shroud around the nozzle fixed at oneend to the unit remotely from the outlet end of the nozzle, an annularchannel, radially inwardly directed, mounted on the other end of saidtubular shroud at the nozzle outlet, and an obtnrator for the nozzleoutlet in the form of pair of calliper arms slidably mounted in saidchannel movable towards each other transversely across said nozzleoutlet to partially overlap the inner periphery and effectively restrictthe cross-sectional area thereof, in order to constrict the jet, wherebythe said tubular shroud, annular, channel, and obturator accordinglyleave the nozzle free for thermal expansion and contractionindependently of the said obturator with its said associated parts.

6. A jet pipe unit according to claim 5, means wherein the said tubularshroud has its end remote from the Cit outlet end of the nozzlesubstantially coincident with the other end of the nozzle and includingmeans for adjustably securing those said ends of nozzle and shroud tothe rest of the jet pipe.

7. A jet pipe unit according to claim 5 including a flange on the end ofthe nozzle remote from its outlet, a flange on the same end of thetubular shroud and means for bolting these flanges together to the restof the jet pipe.

8. A jet pipe unit according to claim 5, including within said annularchannel, carbon inserts against Whicl bears the adjacent relativelyslidable face of each of H3 said calliper arms.

Pi-eierences (Iited in the file of this patent UNiTED STATES PATENTS2,516,909 Redding et al. Aug. 1, 1950 Johnstone et a]. Aug. 28, 19512,597,253 Melchior May 20, 1952 2,693,060 Brown July l5, 1952 2,693,062Weiler et al July 15, 952 2,608,053 Davidson Aug. 26, 1952 FOREIGNPATENTS 316,601 Great Britain Aug. 1, 1929 9l9,004 France Feb. 25, 1947(Corresponding U. 5. 2,565,854, Aug. 28, 195i)

